
PRESENTED BY 

THE EASTERN PAVI NG BRICK CO. 

catskilln.y. 




























































































































































































Sc OOf . 3 COPY, 

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LIBRARY OF CONGRESS, 

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Chap,.Copyright No._ 

Shelf.iK.3__6 

UNITED STATES OF AMERICA. 
















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VITRIFIED BRICK 

FOR 

STREET PAVEMENTS 

A Description of its Manufacture and 
Some Notes on its Use 

FREDERIC A/KUMMER, C.E. 

H 9 

JUNl MEM. AM. SOC. C. E. 


CATSKILL, N. Y. 

THE EASTERN PAVING BRICK COMPANY 

1899 

All rights reserved 

N. Y, OFFICE 
1312 EMPIRE BUILDING 






33182 

COPYRIGHT, 1899, BY 

THE EASTERN PAVING BRICK COMPANY 


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PREFACE 


In presenting this little work on the manufacture 
and use of vitrified paving brick, it is our desire to 
point out, concisely and clearly, the many advantages of 
such brick as a street paving material. Besides at¬ 
tempting to show how such brick are manufactured, as 
well as the extreme care required in their manufacture, 
we give some information as to the manner of laying 
brick pavements, which will be of use to those who de¬ 
sire to secure from this material the best results. 

Vitrified brick has sometimes been condemned for 
street paving because the work of laying it has been im¬ 
properly done, the brick itself being charged with a 
fault which was due to the manner in which it was laid. 
Poor foundation, lack of care in selecting the materials, 
and, most usual of all, improper or insufficient grout¬ 
ing of joints, invariably produce a poor street. If, as 
a result of such work, the brick itself is criticised, such 
criticism must be attributed to ignorance as to how a 
brick pavement ought to be laid. Vitrified brick, if 
laid so as to secure the best results, seldom wears out, 
provided, of course, that the brick itself is of thoroughly 
good quality. It will be seen, however, that the mak¬ 
ing of vitrified brick is an operation requiring a high 
degree of skill in order that the product may meet the 
exacting conditions under which it is to be used. 




THE MANUFACTURE OF PAVING BRICK 


AT THE 

Plant of The Eastern Paving Brick Co. 


The works of The Eastern Paving Brick Company 
are located at Catskill, on the Hudson River. Extensive 
docks give this company especial advantages for water 
transportation, and enable it to deliver its product con¬ 
veniently and at small cost to all points available from 
tide-water. The land owned by the company, including 
its clay and shale banks, comprises about four .hundred 
acres. The material is procured some ten miles from 
the works. It consists of low-grade iron-ore, shale, and 
clay. By efficiently combining these materials in the 
proper proportions a mixture is obtained which pos¬ 
sesses the elements necessary to produce a tough, homo¬ 
geneous vitrified brick, retaining its shape at very high 
temperatures and proving extremely durable in service. 
This company manufactures and ships about twenty- 
five million vitrified brick annually, which are sold in 
the Eastern towns and cities for street paving and sewer 
work. In order to manufacture this large number of 
brick, an investment of about five hundred thousand 
dollars has been made in real estate, buildings, kilns, 
machinery, docks and general equipment. To operate 



6 


this plant at its full capacity, machinery having a ca¬ 
pacity of more than one thousand horse-power is 
required. 

The selection of the materials and their analysis and 
proper combination require constant watchfulness, as 
much depends upon the care with which the ingredi¬ 
ents are combined. In preparing the material for use, 
the following method is adopted: the shale and clay are 
brought to the works in hopper cars and conveyed 
upon an overhead trestle into the Storage Building. 
Here the cars are dumped, the shale and clay being kept 
separate in order that the former may first be run into 
the dry pans by means of conveyer belts. These dry 
pans consist of heavy rollers revolved in a pan having 
perforated plates at its outer diameter. The shale is here 
reduced to a fine powder, which falls through the per¬ 
forations in the bottom of the pan at its outer edge, and 
is then taken up by the buckets of a lifting machine 
and carried into the second story of the Storage Build¬ 
ing, where it is passed through fine screens, that portion 
which has been sufficiently pulverized being deposited 
in storage bins. It has then reached the consistency of 
fine dust. The coarser material returns again to the dry 
pans to be re-ground and screened as before. From 
these storage bins chutes convey the powdered shale to 
the Mixing Room, where the materials entering into 
the composition of the brick are weighed and measured 
by automatic devices. This arrangement secures an 
accurate proportioning of the ingredients, which pro¬ 
duces a homogeneous and uniform product. 


7 


After being weighed and measured the material 
passes into the first of the mixing machines, called pug 
mills, where the shale and clay are thoroughly 
mixed while dry. It is then carried on conveyer 
belts into the Manufacturing Room, where it passes 
through other mixing machines in which a suffi¬ 
cient amount of water is added to combine the in¬ 
gredients. This mixing is done under high pressure 
in order to insure the perfect blending of the com¬ 
ponent parts. The material then passes into the brick 
machines, which are operated upon the semi-dry proc¬ 
ess and are of the auger type, producing side-cut 
brick. Here it is again subjected to high pressure as it 
is forced through the steel dies of the machines. These 
dies are lubricated by steam. The clay issues from the 
dies in a solid column and is carried on conveyer belts 
through the cutting machines, where it is automati¬ 
cally cut up by wires into bricks of the size desired. 
This process produces what are known as wire-cut 
brick. 

The bricks are then carried, still on belts, to the re¬ 
pressing machines. Here they are taken from the 
belts by hand and passed into the repressing machines, 
where they are subjected to heavy pressure, which 
rounds the corners and edges, making what is known 
as repressed or bevel-edged brick. Such of the brick 
as it is not desired to repress are allowed to pass along 
on the belts without being thrown into the repressing 
machines. The brick of both grades are finally placed 
upon small iron cars, upon tracks on each side of the 


8 


repressing machines, which connect with other tracks 
leading to the Drying Rooms. These rooms are lo¬ 
cated at the end of the Manufacturing Room, and the 
cars are run from one room to the other directly and 
conveniently without loss of time. 

The heat for drying the brick is obtained from the 
kilns as they cool, by means of underground conduits 
leading from the front and back of each kiln to the 
Drying Rooms, circulation being secured by means of 
large blowers located on each side of the drying build¬ 
ing. These blowers serve to draw the hot air gently 
and slowly from the kilns (mixing it with cool air, if 
necessary, to temper the heat) and deliver it to the Dry¬ 
ing Rooms. While each kiln is being fired a temporary 
wall is built between it and the hot air conduit along¬ 
side. When it is desired to cool the kiln this wall is 
knocked away and circulation of the air is effected be¬ 
tween the kilns and the Drying Rooms by means of the 
blowers. « 

In the Drying Room the brick are thoroughly dried 
before being placed in the kilns. It is necessary that 
the brick should be absolutely free from moisture, 
otherwise they would crack and split upon the appli¬ 
cation of heat in the kilns. After they are so dried, 
the cars containing them are carried on tracks out at 
the further end of the drying building, which com¬ 
prises a series of long tunnels leading from the Manu¬ 
facturing Room to the kilns. The cars are conveyed 
from these tunnels directly into the kilns, where the 
brick are stacked up preparatory to burning. There is 


9 


no re-handling of the brick from the time they are 
placed on cars in the Manufacturing Room until they 
reach the kilns. 

The stacking of the brick in the kilns must be care¬ 
fully done. Sand is placed between them to prevent 
them from sticking together when subjected to great 
heat. After the kiln is filled with its charge of 150,000 
brick, it is walled and sealed up at both ends. Fires are 
then kindled in the ovens on each side. The kilns are 
what are known as down-draft kilns, because the heat 
from the ovens passes upward into the dome of the kiln 
and then down through the entire mass of brick into 
underground flues leading to smoke-stacks at the side. 
The process of burning is gradual and covers a period 
of some ten days. The greatest care is necessary to 
produce gradually the degree of heat desired. The 
burning must be regular and gradual, the heat being 
increased slowly to the maximum temperature. The 
temperature is steadily augmented for a period of five 
days until the maximum temperature is reached, when 
it is maintained as nearly constant as possible for five 
more days, to enable the heat to penetrate throughout 
the mass of brick. The firing is then discontinued and 
the kiln is allowed to cool slowly. After the brick are 
burned and cooled sufficiently, the kiln is opened. 

After being removed from the kilns the brick are 
carefully sorted, and any which from their location in 
the kiln may have been under-burned or over-burned 
are separated from the others. These latter brick are 
used for building purposes, sidewalks, etc., and only 
the best selected brick are sold for street paving. 


10 


COMPOSITION OF CATSKILL PAVING 

BRICK. 

The term vitrified brick as applied to paving brick is 
in one sense a misnomer. Paving brick are not com¬ 
pletely vitrified. Were they so, they would be brittle, 
glassy, and entirely too hard for street paving. They 
are partially vitrified, however, and it is necessary that 
the ingredients be so selected that this partial vitrifica¬ 
tion may be readily accomplished without employing a 
temperature so high as to impair the shape of the 
brick. The composition of such brick is about as 
follows: 65 to 70 per cent, of silica, 18 to 20 per cent, 
of alumina, 10 to 12 per cent, of oxide of iron, 3 to 
4 per cent, of lime, and a small percentage of the 
alkalies which are found in most native clays. The 
composition of course varies with the different makes 
of brick. The superior results which the Catskill brick 
have shown in service and in tests are due to the fact 
that the materials used are capable of being perfectly 
blended. The silica and alumina shown in the analysis 
are necessary to form the skeleton of the brick. The 
iron, lime, and alkalies are fluxed, and the iron, melt¬ 
ing at a lower temperature than the silica and alumina, 
fills the interstices between their particles, thereby 
cementing the mass together. If an excessive propor¬ 
tion of iron be used, it will prevent the particles of 


II 


silica from touching each other, thereby causing the 
brick to lose their shape, stick together, and become 
warped and cracked. This may be illustrated by com¬ 
paring the process of making brick to the process of 
making mortar. The mason mixes a sufficient amount 
of lime with sand in order to fill up the interstices; he 
then applies water to the mixture of sand and lime, and 
fills the smaller interstices which remain after the lime 
is incorporated in the mass of silica; he then adds 
still more water, until finally he prevents any of the 
particles of silica from touching each other, when he is 
enabled to handle the mortar with his trowel or hoe 
with ease. So soon as the water evaporates from the 
pile of mortar, the mason will discover that it has 
hardened and that he can no longer handle it with his 
trowel. He must then add more water in order to 
prepare the mortar for use. An insufficient amount of 
iron in the brick results in incomplete filling of the 
interstices, just as when there is too small an amount 
of water in the mortar. On the other hand, an exces¬ 
sive amount of iron causes the brick to lose their shape, 
just as an increased amount of water in the mortar 
makes it possible to handle it with the trowel easily. 


12 


Tests of Catskill brick show results about as % follows: 

Tests of Catskill Paving Brick made at the Laboratory 
of Lathbury & Spackman, in Philadelphia, in ac¬ 
cordance with the Requirements of the Specifications 
of the National Brick Manufacturers Association.: 

Catskill shale paving 
bricks from H unter Ave¬ 
nue and Colby Street 
(Albany, N. Y.), May 


25. *8y8. 

Average size in inches. 8.625X4.00X 2.50 

Average weight in pounds. 7.071 

Average area of top surface, square inches, 21.56 

Average volume of one brick, cubic inches, 86.25 

Average specific gravity . 2.41 

Absorption of water, average of 5: 

Weight in pounds, after drying 48 hours.28.25 

Weight in pounds after immersion 48 hours.28.92 

Weight in pounds of water absorbed. 0.67 

Percentage of water absorbed . 2.37 

Cross breaking strength, bricks on edge. Centre load between 

supports 6 inches apart: 

First . 8,640 lbs. 

Second . 9,390 

Third . 9,800 

Fourth . 9,900 

Fifth . 10,940 

Sixth . 11,080 

Seventh . 11,380 

Eighth . 12,550 

Ninth . 13,080 

Tenth . 13,920 


Average strength in pounds . ii,077±i,6ii 

Modulus of rupture . 2,492 






















*3 


Impact tests {two), 28-inch rattler, 20 inches long, making 30 

revolutions per minute. 


(1) (2) 

Weight before tests, pounds . 156.20 153.71 

Weight after 300 revolutions . 148.59 147.14 

Weight after 1,800 revolutions. 133-37 130.53 

Loss in pounds after 300 revolutions. 7.61 6.57 

Loss in pounds after 1,800 revolutions. 22.83 23.18 

Loss in per cent, after 300 revolutions. 4.87 4.27 

Loss in per cent, after 1,800 revolutions. 14.62 15.08 


Average per cent, loss after 1,800 revolutions.. .. 14.85 


Owing to the superior quality of these brick they 
have come to be extensively used in the Eastern cities. 
The following figures compiled from the records of the 
company show where their brick have been laid and in 
what quantities during the past few years: 


STATEMENT OF CATSKILL BRICK IN USE 
IN THE FOLLOWING PLACES. 


New York (State): 

Albany. 

Brooklyn. 

Mount Vernon 

New York . 

Patchogue, L. I.... 

Tarry town . 

Johnstown . 

Catskill . 

Troy .. 

Jamaica, L. I. 


196,589.7 square yards. 


77,303 

35,541 


ii 

a 

ii 

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12,000 


ii 


14,693 

3.100 

6.100 
1,600 

26,890 


55,ooo 


ii 




















14 


Ilion .• 

Port Chester .• 

Poughkeepsie . 

Glens Falls. 

New Rochelle (railroad tracks)... 

Schenectady. 

Groton . 

Water Filter at Albany. 

Water Reservoir at Poughkeepsie.. 

New Jersey: 

Newark . 

Perth Amboy . 

West Orange . 

Jersey City.• 

Massachusetts: 

Holyoke .. 

Fitchburg . 

Connecticut: 

Waterbury . 

Stamford . 

Norwalk . 

South Norwalk .> 

Vermont: 

Burlington . 

Montpelier ..• 

Rhode Island: 

Newport . 

West Indies: 

Kingston, Jamaica . 


136 square yards. 

4,350 
5,800 
7,168 
32,150 
21,373 
230 

1,820,318 brick. 

252,400 


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19,665 square yards. 
1,000 
150 
5,740 


it 


it 


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13.800 square yards. 
2,140 

700 square yards. 

7.800 “ 

4,5oo “ 

2,900 “ 


3,600 square yards. 
200 


a 


1,100 square yards. 


15,000 square yards. 























Extract from the Annual Report of the City Engineer of A/bany, N. Y.,for the year ending 
January i, 1899, showing the great increase in the use of vitrified bricky and the decrease 
in the use of other paving materials. Of the total area of brick paving, 196,589 square 
yards is laid with Catskill brick. 

Area of Pavement Laid Each Year from 1885 to 1898. 


15 




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Granite covered with asphalt, to be deducted from granite area. 























































































i6 


PAVING MATERIALS. 

The question of properly paving streets is one 
which has not until recently received that careful at¬ 
tention and study on the part of engineers and munici¬ 
pal authorities which the interests involved demand. 
It is a question of more than ordinary importance, in¬ 
volving the health, comfort, and safety of the com¬ 
munity, as well as considerations of durability, and of 
economy, both as to first cost and as to maintenance. 

It may be stated as a general proposition that the 
first requisite to a street pavement is that it afford a 
safe and agreeable roadway for horses and vehicles. By 
an agreeable roadway we mean not only one which is 
pleasant to those driving over it, but also one which 
facilitates the traction of loaded vehicles as much as 
possible without being slippery or unsafe. A further 
consideration to be borne in mind is that the pavement 
be so constructed as to be durable. Having conserved 
these two requirements, we have gone a long way tow¬ 
ard solving the problem of a satisfactory pavement. 

There are also certain other considerations which, 
while they are of less importance, nevertheless largely 
enter into the selection of a paving material. The 
pavement should be as nearly noiseless as possible; 
it should be sufficiently low in cost to warrant its 
use, and it should be so laid that sections may be re¬ 
moved when necessary without great cost and without 


*7 


impairing the value of the surrounding pavement. It 
should further be of such a nature that it will not ab¬ 
sorb liquids, gases, or street filth. It is also of great 
importance that pavements be so constructed that, 
while sufficiently hard and rigid to enable them to sus¬ 
tain the heaviest loads, they will at the same time not 
be so hard as to injure the feet of horses. 

A street pavement is made up of several component 
parts, each having its own function. The foundation 
gives to the pavement the strength and rigidity neces¬ 
sary to withstand heavy loads and the continual im¬ 
pact of traffic. Upon this should be placed a properly 
cushioned bearing surface which does not primarily 
support the loads, but serves to transmit the weight of 
these loads to the foundation. This bearing surface 
must be smooth and lasting. Unless, however, the 
pressure be properly distributed over the sub-grade, 
by the foundation, the best paving materials are of 
little value. 

Bearing in mind, then, that the function of the foun¬ 
dation is to transmit the weight of passing loads to the 
ground beneath, and that of the pavement proper to 
receive these loads and properly transmit them to the 
foundation, at the same time affording a safe, smooth, 
and durable pavement, we are led to the consideration 
of the question: what material will best answer this 
purpose? The opinion is wide-spread among en¬ 
gineers and others interested in street paving—and 
this opinion is rapidly becoming more general—that 
vitrified brick most nearly fulfils these requisites. (See 


table on page 15.) Before outlining the reasons for 
this it may be well to state briefly wherein such brick 
differs from the common building brick. This differ¬ 
ence results first from its having been subjected to a 
temperature sufficiently high to produce what is called 
vitrification, and, secondly, from the fact that it is com¬ 
posed of ingredients which make the process of vitrifi¬ 
cation possible. Ordinary building brick, being made 
of clay which does not contain these ingredients, will 
crumble if subjected to the heat required to effect the 
process of vitrification. Vitrified brick, if well made, 
are hard without being brittle; tough and able to re¬ 
sist impact without splitting, chipping, or crumbling; 
so dense that they absorb only a small percentage of 
moisture and hence are not affected by the frost; and 
are homogeneous in quality so that they will wear 
smoothly and evenly over their entire surface. Such 
brick can only be produced by the most careful manip¬ 
ulation of the ingredients and by the exercise of a high 
degree of skill and judgment in the burning. Many 
so-called vitrified brick, which through lack of proper 
care in the manufacture are not suitable for paving 
streets, have been placed in the market, to the great 
detriment of paving brick in general. 

As regards the foothold afforded to horses by brick 
pavements, it may be claimed, without fear of contra¬ 
diction, that brick, especially on grades, affords a better 
foothold and involves less danger of slipping than either 
asphalt or granite block, particularly after the latter has 
been subjected to traffic for considerable time and has 


19 


become polished and rounded. The reason for this is, 
in the first place, that the rounded edges of repressed 
brick and the joints between them afford a series of 
parallel grooves, two and a half inches apart (being the 
thickness of the brick), which extend laterally across 
the street and afford an opportunity for the calks of the 
horses’ shoes to secure a hold. This effect is not ob¬ 
tained with asphalt or asphalt block, and, while it is 
obtained with granite block when first laid, the latter 
soon becomes polished, and is then even more slip¬ 
pery than asphalt. On the contrary, no matter how 
much a brick pavement wears, the surface does not be¬ 
come polished. Swan Street, in Albany, N. Y., is an 
instance of a heavy grade laid with brick. This is 
about a nine per cent, grade, and at the top is located 
one of the large engine-houses of the Albany Fire De¬ 
partment. The engine drivers have found, in getting 
their heavy machines up and down this grade in all 
weathers, that the slipping is noticeably less than upon 
any other kind of pavement in similar use in that city. 

Greater ease in traction is one of the chief advan¬ 
tages of a brick pavement. Even on slight grades, 
horses experience difficulty in pulling loads of any 
weight, unless their foothold is sure. This ease of 
traction is the same in very warm weather as in cold 
weather, because changes of temperature do not affect 
brick. It is well known that the softening of asphalt 
in hot weather makes traction, especially in the case of 
heavily loaded vehicles, extremely difficult. We have 
all, doubtless, seen cases where the wheels of wagons 


v 


20 


have cut into the hot asphalt surface to a considerable 
depth. Such a pavement also becomes injurious to 
horses in very warm weather on account of its ten¬ 
dency to hold the heat. Similar results are found in 
wet weather, when difficulty of traction is caused by 
the insecure foothold which horses obtain, and in cold 
weather the asphalt becomes so hard that it polishes 
almost like granite block and becomes exceedingly 
slippery. These facts are well known to all who are 
familiar with asphalt pavements. 

In small towns where the roads are built of macadam 
or other similar material, brick will be found of the 
highest value for paving the gutters along the sides of 
the roadways. Many towns and villages have adopted 
brick for this purpose and find it in every way superior 
to cobble-stones or to Belgian block. It not only af¬ 
fords a smoother surface for running water, but makes 
a handsomer finish to the street. At the same time its 
cost is as low as and in many cases considerably lower 
than second-hand Belgian block, and is not much 
higher than that of ordinary cobble-stone. 

As a material for use between the tracks of street 
railroads, even where cheaper material may be em¬ 
ployed in the street itself, brick has no equal. A well- 
constructed brick pavement, with pitch joints to pro¬ 
vide against the vibration of the ties, makes a smoother 
and better finished track and costs less to lay and to 
maintain than any good material known. It presents 
none of the objectionable features found in asphalt or 
Belgian block. 


21 


THE SELECTION OF PAVING BRICK. 

Leaving out of consideration the quality of the brick, 
the first question to be decided is that of size. Oc¬ 
casionally brick for street paving is made no larger 
than ordinary building brick, 2 in. by 3 in. by 8 in. 
Others again are 2 1-2 in. by 4 in. by 8 1-2 in., the size 
varying up to a block 3 in. by 4 in. by 9 in., or even 4 in. 
by 5 in. by 12 in. Again, the question is between fire¬ 
clay brick, shale brick, or a brick which is a combina¬ 
tion of the two; and, as these bricks differ widely in 
color, many persons make this a consideration in de¬ 
termining the kind of brick to be selected. That a 
brick is said to be vitrified, or that it has been specially 
burned for street paving, does not necessarily make it 
suitable for this purpose. Some brick, especially those 
which are most thoroughly vitrified, are too hard to be 
used in a street; and, while such brick may show good 
results in tests on account of their hardness, they are 
so brittle that they chip and crack readily under the 
impact of horses’ feet. Again, the desirability of a 
square-edged brick, or one which has been repressed 
and has rounded or bevelled edges, must be considered. 

It is generally conceded that a brick 2 1-2 in. by 4 in. 
by 8 1-2 in. is most satisfactory for general paving 
work. This size has been adopted by the National 
Brick Manufacturers’ Association as the standard. 
Smaller brick do not look well and are troublesome to 
handle; at the same time they involve a needless 


22 


number of joints to be filled with cement. The cement 
is not so durable as the brick and therefore the dura¬ 
bility of the pavement as a whole is reduced. This 
might seem to be an argument in favor of paving 
blocks of the largest size, but, in burning such blocks, 
it has been found very difficult to insure thorough vitri¬ 
fication. A paving brick, of the standard size men¬ 
tioned, may be thoroughly vitrified, giving it a homo¬ 
geneous and uniform texture, while a paving block, on 
account of its greater size, is often found to be soft at 
the centre. By this vitrification we mean the partial 
vitrification which is desirable in paving brick. Ex¬ 
perience in the manufacture of vitrified brick has 
shown that not more than eighty per cent, of the prod¬ 
uct of the kilns in the manufacture of vitrified brick is 
suitable for use in street paving. The remaining twenty 
per cent, is, however, merchantable, inasmuch as brick 
of the size mentioned above are readily salable for other 
purposes than street paving. This makes it for the 
manufacturer’s interest to cull his brick carefully. In 
the case of block the culled material is not readily salable 
for other purposes and hence there might be a ten¬ 
dency to cull such brick less rigidly. 

The form of paving brick in most general use is the 
bevel-edge or repressed brick. This bevelling of the 
edges makes a round shoulder which does not chip off, 
a fault sometimes found with square-edged brick. At 
the same time, there are many advocates of the brick 
with square edges who believe that, if the joints be¬ 
tween the brick are thoroughly filled to the top with 


2 3 


hard Portland-cement grout, the cement will sustain 
the square corner of the brick and prevent its chipping 
off. This is probably true early in the life of the pave¬ 
ment; but, after the brick begins to wear down, the cor¬ 
ners generally become chipped or ground off into the 
rounded form which the bevel-edge brick has when 
laid. The joint between the bricks which is secured 
by the rounding of the corners is desirable, providing a 
foothold for horses, as above stated. The lugs or 
other projections sometimes employed are not neces¬ 
sary, as an ample joint may be secured without them. 
There are some, however, who prefer the lugs, owing 
to the greater regularity obtained in the joints. 


LAYING THE BRICK. 

FOUNDATION. 

The first thing to be considered in laying a street 
with brick is the foundation, and this is of the utmost 
importance. After the street has been reduced to 
grade, the earth should be thoroughly rolled and 
tamped until the surface of the road-bed is firm, hard, 
and compact. If any depressions occur under the roll¬ 
ing they should be properly filled in with sand or other 
suitable material and re-rolled. If the character of the 
ground renders it necessary, an efficient method for 
draining the soil under the foundation should be 
adopted. Upon this hard-rolled surface is to be laid 
the foundation, which is to support the paving surface. 


24 


This generally consists of a layer of concrete from four 
to six inches deep. In some cases a very durable pave¬ 
ment may be formed by laying the brick upon a bed of 
thoroughly rolled sand. In other cases broken stone, 
cinders, etc., may be used. A sand foundation in lo¬ 
calities where the underlying soil is hard, clean sand, 
containing little or no loam, is proving highly satis¬ 
factory in many cities along the southern coast as well 
as in the West. Miles of streets have been laid upon 
the sand-bed, the same being thoroughly wet and rolled 
until it becomes as solid as a floor. Upon this the 
brick is laid without any other joints than those of 
clean, sharp sand, and such a pavement, with the sand 
foundation confined between the curbs, needs only 
careful maintenance, at a slight cost, to make it thor¬ 
oughly durable and satisfactory. This pavement, how¬ 
ever, can only be recommended for light traffic and 
where the draining of the sub-grade can be depended 
upon. The general practice, particularly in the North 
and East, is to use concrete foundation, owing to the 
character of the soil, and the heavy traffic to be sus¬ 
tained. The concrete for this purpose is generally 
composed of one part hydraulic cement, two parts 
clean, sharp sand, and five or six parts broken stone. 
The cement and sand are mixed dry and then made 
into mortar, after which broken stone, thoroughly 
wet, is mixed in. This foundation is spread evenly 
over the surface and thoroughly rammed. It should 
be protected from the sun while drying by being moist¬ 
ened or covered with a layer of sand. The sand cush- 


2 5 


ion and the brick should not be placed upon it until 
after it has dried for a considerable time, from one to 
two weeks if possible, although in many cases only 
forty-eight hours is allowed for drying. The greatest 
care should be taken to insure good material and 
proper workmanship in constructing the foundation. 
If this is not well done it will produce faults in the pave¬ 
ment which can only be remedied at great expense. 

The sand cushion is a layer of sand which is gen¬ 
erally placed on top of the concrete to form a bed for 
the brick. Practice regarding the depth of this layer 
of sand varies considerably. In some cases it is only 
i 1-2 inches deep, varying from this up to 2 1-2 and 
even 3 inches. A cushion of this character is very de¬ 
sirable, inasmuch as it not only forms a perfectly true 
and even surface upon which to place the brick, but it 
also acts as a cushion and makes the pavement less 
hard and rigid than would be the case were the brick 
set directly upon the concrete. Upon the sand cushion 
the brick are laid on edge, joints being properly 
broken. The sand cushion, forming the bed on which 
the brick are laid, is wet, smoothed, and brought to the 
proper crown in the centre of the street by means of 
wooden templates, properly trussed, mounted on 
wheels or shoes which bear on the upper surface of the 
curb. Advancing the template along the street levels 
and trues the sand-bed to its proper shape. The brick 
are then placed on edge, broken joints being formed 
by placing half brick at the curb, the brick at the curb 
line being placed loosely against the curb, so that when 


26 


the pavement is rolled the brick have room to spread 
and settle into the sand-bed. This obviates the dan¬ 
ger of forming an arch leaving a hollow space under 
the brick, between the bricks and the concrete. Such 
a hollow space will result in the rumbling noise some¬ 
times heard upon improperly laid brick streets. The 
rolling of the brick before grouting is generally done 
with a heavy cylinder roller weighing about one ton to 
each foot of its length. Rolling should be continued 
until all brick are properly embedded in the sand 
cushion. 

THE JOINTS. 

There is some diversity of opinion as to the best 
material to be used for the joints between the brick 
in street paving. The three materials most commonly 
used are clean, sharp sand, paving cement (being a 
combination of asphalt, pitch and other ingredients) 
and Portland-cement grout, composed of the best 
grade of Portland cement and clean, fine, sharp sand, 
the finer the better. Each material has some advan¬ 
tages, and each must be properly used in order that 
satisfactory results may be obtained. A street poorly 
grouted with Portland cement is considerably worse 
than one which is not grouted at all but which has its 
joints filled with clean, sharp, dry sand. It is to be 
particularly noted that in brick paving, aside from the 
quality of the brick, the joints are the most important 
factor in the life of the pavement. As soon as a num¬ 
ber of brick in a street settle below those immediately 


27 


surrounding them because of badly made joints, the 
tendency of traffic over such a spot is to grind off the 
exposed edges of the brick, and in a little while a de¬ 
pression in the street is formed where the brick are 
badly broken or chipped, making it appear to the ordi¬ 
nary observer that the fault was in the brick. The 
same brick, if the joints had been good, would have 
worn indefinitely. 

Portland-cement grout makes a very satisfactory 
joint when properly applied, and, by giving a good 
support to the edges of the brick, reduces the danger 
of chipping to a minimum. We cannot lay too much 
stress upon the proper application of the cement joint. 
As usually applied, the cement is mixed with clean, 
very fine, sharp sand, and water, and when reduced to 
the consistency of ordinary thin grout, is generally 
flooded upon the pavement from the mixing-box and 
swept into the joints between the brick with brooms. 
This method is very undesirable. It will be found that 
in many cases the sand, especially where it is not as 
fine as it should be, gets away from the cement while 
the grout is being spread over the street, resulting in 
joints which are some all sand, some all cement, and 
none properly made. Much the more satisfactory way 
is to pour the joints, the grout thoroughly mixed being 
dipped out of the mixing-box with pails, the mixture 
being constantly stirred until it is all dipped out of 
the box. This method of pouring the joints secures 
an even and well-filled joint which will add very 
greatly to the life of the pavement. The sand and 


28 


cement should be carefully mixed and should remain 
uniform. If coarse sand is used it separates from 
the cement during the operation of filling the joints 
and chokes up the joint with wet sand and very 
little cement, while other joints will be filled with ce¬ 
ment and little or no sand. As a consequence, those 
joints which are choked up are not filled to the bottom, 
the coarse sand not having the consistency to run down 
between the brick to the sand cushion. Thus no bond 
is formed between the bricks and they soon separate 
from each other under traffic, and the pavement shows 
great wear at these points. It is easy to see, in going 
over a street, where the grouting has been well done 
and where improperly done. Portions of the pave¬ 
ment, sometimes as small as one square yard, or less, 
with little or no cement in the joints, and showing great 
wear, are evidences of improper grouting. 

Joints are sometimes made by mixing the sand and 
cement dry and heating them. The mixture is then 
broomed into the joints until they are filled, after which 
the pavement is wet down, forming the bond after the 
sand and cement are in place. The ordinary method, 
however, of pouring the grout, gives thoroughly satis¬ 
factory results when carefully done. 

The paving-cement joint is somewhat more ex¬ 
pensive than that made with Portland cement. In 
places where the pavement is subjected to great vibra¬ 
tion, such as in railroad streets and adjoining rail¬ 
road tracks, it preserves the integrity of the pavement 
better. This is because the paving-cement joint is 


29 


elastic and allows a certain amount of play between 
the individual bricks without destroying the joint be¬ 
tween them. The usual composition, which is used 
at a temperature of 300 degrees Fahrenheit, consists 
of 20 parts of refined asphalt, 3 parts of residuum oil, 
and 100 parts of coal tar obtained from the direct 
distillation of coal tar, generally known at the works 
as No. 4. The joints should be as completely filled 
with this material as possible, and to effect this it must 
be used only when very hot. Engineers frequently in¬ 
sist upon the paving cement being poured into the 
joints from a pot having a spout; but a much better 
joint is obtained by pouring the material over the 
street from coal hods and brooming it into the joints 
with wire brooms. To do this successfully a heating 
tank on wheels is necessary, holding about ten barrels. 
This tank should be kept hot all day. One man is 
necessary to feed the fire and draw out the mixture 
from a spigot into coal hods. Another man carries the 
hods from the heating tank to a third, who pours the 
hot material over the street. The latter starts to pour 
in the centre of the street, working backward toward 
the curb and pouring a strip about two feet in width. A 
fourth man with a wire broom follows immediately 
after him sweeping the surplus material toward the 
pourer and in the direction of the curb. This method, 
when properly employed, leaves the entire surface 
of the street covered with a very thin coating of the 
pitch. Upon this a light coating of sand is at once 
spread. This sand being placed on the hot pitch be- 


3 ° 


comes thoroughly mixed with it, and the traffic over 
the street soon grinds all appearance of the pitch from 
the surface of the brick, leaving the street smooth and 
clean. 


SPECIFICATIONS FOR LAYING BRICK. 

We give below a set of specifications which may 
prove of value to those contemplating brick paving 
work. 

FOUNDATION. 

Sand. 

The sand, wherever mentioned in these specifica¬ 
tions, except for grouting and filling the joints of the 
brick pavement and sidewalks and for covering the 
same, or for the sand cushion for the brick pavement, 
shall be clean and moderately coarse, of the best qual¬ 
ity, and shall be free from loam and refuse matter. For 
the sand cushion for the brick pavement, the sand must 
be screened until entirely free from pebbles exceeding 
one-quarter (1-4) inch in size. For grouting and fill¬ 
ing the joints of the brick pavement and sidewalks, and 
for covering the same, the sand shall be clean and sharp 
and of the best quality. At least eighty per cent. (80%) 
by weight of the first-named sand shall be retained 
by a screen having fifty (50) meshes to the lineal 
inch, so that not more than three per cent. (3%) by 


3i 


weight shall be lost upon washing. The second-named 
sand shall be capable of passing a fifty (50) mesh 
per lineal inch screen, but not less than fifty per 
cent. (50%) by weight shall be retained by a screen 
having one hundred and twenty (120) meshes per 
lineal inch. 

Depth of Concrete. 

After the surface of the carriage-way shall have been 
brought to the proper sub-grade and shall have been 
properly rolled so as to be smooth and practically firm 
and dry, hydraulic-cement concrete, made as herein¬ 
after specified, shall be placed upon it to a depth of 
six (6) inches. 

Concrete. 

The concrete used as a foundation for the pavement 
and which is provided for in the contractor’s bid, shall 
be composed of one (1) part of fresh-ground American 
hydraulic cement, of the best quality, eighty (80) 
pounds weight of such cement being taken as equal to 
one cubic foot in volume, two (2) parts of clean, sharp 
sand and four (4) parts of broken stone, or of broken 
bricks, the pieces of which shall in no case be too large 
to pass through a two-inch ring. The proportions of 
sand, cement, and stone as above described, are to be 
determined by measurement. The cement and sand 
shall be first thoroughly mixed dry; then water shall 
be added by degrees and without flooding the mortar, 
in sufficient quantity to form a stiff mortar; the broken 
stone, previously thoroughly wet, shall next be added 


3 2 


and the mass worked and turned over until the broken 
stone presents surfaces everywhere covered with mor¬ 
tar. The broken stone must be free from dust and 
dirt, but must not have the small-sized pieces screened 
out; it must be passed through a screen or separator, 
and all such stone as will not pass through the two (2) 
inch holes must be discarded and must not be brought 
on the street. The use of broken cobble-stones will 
only be permitted where it is found possible to break 
them into pieces of such size as to absolutely fulfil the 
requirements of this section of the specifications. 

The cement shall be capable of resisting a tensile 
strain of sixty (60) pounds per square inch after thirty 
minutes’ exposure to the air and twenty-four hours’ 
immersion in water, and shall also be guaranteed by the 
makers to have such strength as has been hereinbefore 
required in these specifications; it must be of a well- 
known brand and one that is approved by the City 
Engineer. The use of concrete that has been mixed 
longer than one hour will not be allowed. All mixing 
must be done on tight platforms. 

Concrete shall not be placed on the street unless the 
curbs are previously set and until the bottom has been 
trimmed to exact shape. The depth of the concrete 
shall be regulated by flat iron bars twenty-four (24) 
inches long, one-quarter (1-4) inch thick, and one and 
one-half (1 1-2) inches wide, which shall be driven to a 
firm bearing and have the top of concrete marked 
thereon with chalk, or preferably by means of adjust¬ 
able iron rings with clamping screws. 


33 


The concrete shall be placed in proper position and 
there rammed with heavy rammers until it is thor¬ 
oughly compacted and has a clear mortar surface, 
which surface, when left, shall be six (6) inches above 
the top of the sub-grade heretofore specified, and in 
exact conformity with the drawing of the cross-section 
of the street prepared by the City Engineer. 

At least twenty-four (24) hours shall be allowed for 
the concrete to set before the pavement is laid. When 
connection is made with any layer, set, or partially set, 
the edge of such layer must be broken down and shall 
be free from dust and properly wet, so as to make the 
junction fresh and close. No driving with horses must 
be permitted upon the surface of the concrete at any 
time nor under any circumstances. Careful driving 
will be allowed upon planks placed on the concrete, 
but not until thirty-six (36) hours after the concrete 
is laid. Sand may be brought on the concrete in wheel¬ 
barrows, wheeled on planks laid for that purpose. The 
concrete must be protected from frost by means of 
sand or planks laid thereon, if the weather is cold. All 
concrete injured by frost must be taken up and re¬ 
placed with new concrete. 

Sand Cushion. 

Upon the top of the concrete thus prepared and pre¬ 
viously cleared from all loose stones and rubbish, shall 
be placed clean sand, free from loam, sufficient to form 
five and one-half (5 1-2) inches in depth in connection 
w T ith the brickwork. Particular care must be taken 


34 


that the sand be wet at the time the bricks are laid. 
This sand, as hereinbefore specified, when used as a 
one and one-half inch cushion for the brick pavement, 
must be screened, and free from pebbles of more than 
one-quarter inch in diameter, and must be kept free 
from stones and rubbish after having been spread on 
the concrete. 

Brick Pavement. 

The pavement is to be of repressed, vitrified paving 
bricks of the best quality. The bricks are to be of uni¬ 
form size and quality throughout the entire work. 
They must not be less than two and one-quarter (2 1-4) 
inches wide across their upper and lower faces; not 
less than four (4) inches deep; and not less than eight 
(8) inches long, except where half bricks are necessary 
to fill out lines of pavement. The bricks must be of 
uniform size and of the same manufacture through¬ 
out the entire street. 

All paving bricks must be homogeneous and com¬ 
pact in structure, free from loose lumps of uncrushed 
clay, from laminations caused in the process of man¬ 
ufacture, or from fire cracks or checks of more than 
superficial character or extent. All bricks so distorted 
in burning as to lie unevenly in the pavement shall be 
rejected. Bricks that are improperly annealed will not 
be accepted. 

Tests. 

All bricks shall be free from lime and magnesia in the 
form of pebbles and shall show no signs of cracking or 


35 


spawling, on remaining in water ninety-six (96) hours. 
They shall be subjected to the standard test for abra¬ 
sion, as recommended by the convention of the Na¬ 
tional Brick Manufacturers’ Association, held at Buf¬ 
falo, N. Y., in February, 1897, and under such test shall 
not sustain a loss in weight of more than twenty (20) 
per cent. 

They shall have a specific gravity of not less than 
two and three-tenths (2 3-10). 

They shall absorb not more than five (5) per cent, of 
water when dried at boiling heat of water for forty- 
eight (48) hours and afterward immersed for forty- 
eight (48) hours in water. This test is to be made on 
bricks that have previously been subjected to the abra¬ 
sion test. 

They shall show a modulus of rupture of not less 
than two thousand (2,000) pounds per square inch 
when tested in full size on their edge, or as laid in the 
pavement, the same to be computed by the formula 
•? / 21) 

R = —r; in which formula R is the modulus of rupture, 

2 bd % 

l the length between supports (equal to 6), b and d the 
breadth and depth, all in inches, and w the load, in 
pounds, producing rupture. 

All bricks tested shall show an average equal to the 
limits named above, or, where limits are not named, 
the results of the tests shall be satisfactory to the City 
Engineer, but a variation in individual specimens of 
not to exceed fifteen (15) per cent, of the above limits 
will be allowed. Bricks not hitherto successfully used 



36 


at other places will not be accepted without a chemical 
analysis, certified to by some competent chemist of 
reputation, which analysis shall show a chemical com¬ 
position not differing materially from that of other pav¬ 
ing brick in successful use. All bricks shall have a 
proper shrinkage and shall not differ materially in size 
from the accepted samples of the same make, unless 
such change is due to a change of die, such change to 
be acceptable to the City Engineer; nor shall they 
differ greatly in color from the natural color of the well- 
burned brick of its class and manufacture. These 
qualities shall be compared with the brick deposited 
and referred to at the time of letting or with others 
afterward substituted by the consent of both parties 
to this agreement. 

The bricks will be carefully inspected after they 
are brought on the line of the work, and all lots of 
brick which do not conform in quality and dimensions 
to these specifications will be rejected, and must then 
be immediately removed from the line of the work. 
Where the piles of bricks are mostly of good quality, 
but contain numerous inferior bricks, the contractor 
will be required to furnish such laborers as may be 
necessary to aid the inspector in the examination and 
culling of the bricks; and in case the contractor shall 
neglect or refuse so to do, such laborers as in the opin¬ 
ion of the Street Commissioner shall be necessary will 
be employed by the said Commissioner and the expense 
thus incurred by him will be deducted from and paid 
out of any money that may become due to the con¬ 
tractor under this agreement. 


37 


Proper care must be taken to exclude all poor bricks. 
After the bricks are laid and before they are grouted 
the contractor must remove all inferior bricks that have 
escaped previous culling, including all those marked 
by the inspector as condemned. 

After fifty thousand (50,000) bricks, or such lesser 
number as may suffice to pave the entire street, are 
brought on the ground, the City Engineer shall select 
not less than sixty (60) bricks of apparently average 
quality, which bricks must be packed up for shipment, 
and sent to such laboratory as the said City Engineer 
shall specify, at the expense of the contractor, to be 
tested in the manner hereinbefore described; and if the 
samples so selected fail under the prescribed tests, the 
entire amount of brick shall be rejected and shall be 
immediately removed from the street. No brick must 
be used on the street until the receipt of a satisfactory 
record of tests prescribed. Where a brick of known 
make has already been tested, as herein specified, and 
found satisfactory for other streets, the City Engineer 
may, at his discretion, allow such brick to be used with¬ 
out special tests, reserving, however, the right at any 
time during the progress of the work to reject any lot 
of fifty thousand (50,000) bricks where the bricks do 
not conform to the requirements hereinbefore specified, 
or to any three of such five requirements, or to the sec¬ 
ond requirement alone. 

Paving. 

The bricks are to be laid on edge at right angles to 
the line of the street, except at intersecting streets, 


38 


where they are to be laid at such angle and in such man¬ 
ner as the City Engineer may direct. Each alternate' 
course is to be commenced with a half brick. No half 
bricks or bats are to be used except at the ends of 
courses. All longitudinal joints are to be broken with 
a lap of at least three (3) inches. The joints are to be 
made tight by hammering the courses together fre¬ 
quently and by shoving the bricks together, lengthwise, 
by aid of a crowbar, before the closures are made at the 
ends of the course. The bricks are to be laid by skilled 
workmen, who shall stand on the bricks already laid, 
and in no case shall the bed of sand in front of the pave¬ 
ment be disturbed or walked on after having been 
smoothed over and brought to the exact crown and 
grade. A template shall be used for striking the sand 
cushion to the exact shape of the crown of the street. 
This template shall be made in accordance with the 
plans and directions of the City Engineer; it shall be 
kept whole, true to shape and in good condition; it shall 
rest on the curbs and be drawn forward immediately 
before the bricks are laid. The street is to be swept 
clean before rolling. As soon as practicable, and not 
to exceed three days after the bricks are laid, they are 
to be rolled to a proper surface with a roller weighing 
not less than five (5) tons. Sand is not to be put on the 
pavement until after grouting. After the brick pave¬ 
ment has been properly rolled to the correct finished 
surface and grade, the joints are to be filled with cement 
grout. 


39 


Grouting. 

Grouting is to be of Portland cement of first quality 
and of a brand acceptable to the City Engineer, and of 
such fineness that ninety (90) per cent, will pass 
through a sieve of 10,000 meshes per square inch. 
When mixed neat and exposed one day in air and six 
days in water, it shall withstand a tensile strain of not 
less than 450 pounds per square inch. A pure thin 
Portland-cement grout formed of one part of cement 
to one part of fine, sharp, yellow sand, is to be first 
poured over the pavement, being dipped from a port¬ 
able grout-box, care being taken that it passes into the 
joints and completely fills them. This operation is to 
be immediately followed up with a thicker grout in the 
same proportions of cement and sand, but with just 
water enough to enable it to run, which shall be 
brushed into the joints with a street-sweeper’s bass 
broom, with rubber scraper attached. The pavement 
is to remain undisturbed in this condition until inspect¬ 
ed, then to be completely covered with sand, after 
which the street is to remain closed for not less than 
ten (10) days, and for a longer period if practicable. 
Before the final acceptance of the work, or at such later 
date as the Street Commissioner shall determine, the 
contractor is to thoroughly sweep the street and re¬ 
move all sweepings. The object of the sand covering 
is to prevent the grout from drying out too fast, hence 
it must be sprinkled from time to time in dry and windy 
weather. If from any cause the grout becomes washed 


40 


out of the joints, or does not fill them entirely, at all 
places, the contractor must, before the acceptance of 
his work, thoroughly clean out, wet, and regrout all 
such imperfect joints, and barricade the work from all 
traffic for six days thereafter. During the period of the 
five years’ maintenance of the pavement all open or im¬ 
perfect joints must in like manner be cleaned out, re¬ 
grouted and barricaded. 


SPECIFICATIONS FOR A STANDARD 
METHOD OF CONDUCTING THE RAT¬ 
TLER TEST FOR PAVING BRICK. 

The following from the Report of the Commission 
on Standard Specifications for testing paving brick, ap¬ 
pointed by the National Brick Manufacturers’ Asso¬ 
ciation, will be of value in testing paving brick: 

I. Dimensions of the Machine:—The standard ma¬ 
chine shall be twenty-eight (28) inches in diameter and 
twenty (20) inches in length, measured inside the rat¬ 
tling chamber. Other machines may be used varying 
in diameter between twenty-six (26) and thirty (30) 
inches, and in length from eighteen (18) to twenty-four 
(24) inches; but if this is done, a record of it must be 
attached to official report. Long rattlers may be cut 
up into sections of suitable length by the insertion of 
iron diaphragms at the proper points. 


4i 


II. Construction of the Machine:—The barrel 
should be supported on trunnions at either end; in no 
case shall a shaft pass through the rattling chamber. 
The cross section of the barrel shall be a regular poly¬ 
gon, having fourteen (14) sides. The heads and staves 
shall be composed of gray cast-iron, not chilled or case 
hardened. There shall be a space of one-fourth of an 
inch between the staves for the escape of dust and small 
pieces of waste. Other machines may be used having 
from twelve (12) to sixteen (16) staves; but if this is 
done, a record of it must be attached to the official re¬ 
port of the test. 

III. Composition of the Charge:—All tests must be 
executed on charges composed of one kind of material 
at a time. No test shall be considered official where 
two or more different bricks or materials have been 
used to compose a charge. 

IV. Quantity of the Charge:—The quantity of the 
charge shall be estimated by its bulk and not its weight. 
The bulk of the standard charge shall be equal to fif¬ 
teen (15) per cent, of the cubic contents of the rattling 
chamber, and the number of whole brick whose 
united volume comes nearest to this amount shall con¬ 
stitute a charge. 

V. Revolutions of the Charge:—The number of rev¬ 
olutions for a standard test shall be eighteen hundred 
(1,800), and the speed of rotation shall be thirty (30) 
per minute. The belt power shall be sufficient to rotate 
the rattler at the same speed, whether charged or 
empty. Other speeds of rotation between 24 and 36 


42 


revolutions per minute may be used; but if this is done, 
a record of it must be attached to the official report. 

VI. Condition of the Charge:—The bricks compos¬ 
ing a charge shall be dry and clean, and as nearly as 
may be possible in the condition in which they are 
drawn from the kiln. 

VII. Calculation of the Results:—The loss shall be 
calculated in per cents, of the weight of the dry brick 
composing the charge, and no result shall be consid¬ 
ered as official unless it is the average of two distinct 
and complete tests, made on separate charges of brick. 


SPECIFICATIONS FOR STANDARD METH¬ 
OD OF COMPUTING ABSORPTION TEST 

FOR PAVING BRICK. 

I. The number of bricks for a standard test shall be 
five (5). 

II. The test must be conducted on rattled bricks. 
If none such are available, the whole bricks must be 
broken in halves before treatment. 

III. Dry the bricks for forty-eight (48) hours at a 
temperature ranging from 230 to 250 degrees F. before 
weighing for the initial dry weight. 

IV. Soak for forty-eight (48) hours, completely im¬ 
mersed in pure water. 

V. After soaking, and before weighing, the bricks 
must be wiped dry from surplus water. 


43 


VI. The differences in weight must be determined 
on scales sensitive to one gram. 

VII. The increase weight due to water absorbed 
shall be calculated in per cents, of the initial dry weight. 

Resolved: That in the opinion of the commission, 
any paving brick which will satisfy the requirements of 
reasonable mechanical tests will not absorb sufficient 
water to prove injurious to it in service. We there¬ 
fore recommend that the absorption test be abandoned 
as unnecessary, if not actually misleading. 


SPECIFICATIONS FOR THE STANDARD 
METHOD OF MAKING CROSS BREAKING 
TESTS OF PAVING BRICK. 

I. Support the brick on edge, or as laid in the pave¬ 
ment, on hardened steel knife-edges rounded longitu¬ 
dinally to a radius of twelve (12) inches and transversely 
to a radius of one-eighth inch, and bolted in position so 
as to secure a span of six (6) inches. 

II. Apply the load to the middle of the top face 
through a hardened steel knife-edge, straight longitu¬ 
dinally and rounded transversely to a radius of one-six¬ 
teenth inch. 

III. Apply the load at a uniform rate of increase till 
fracture ensues. 


44 


IV. Compute the modulus of rupture by the for¬ 
mula, 

Sw/ . , . - 

f — ; in which 

2 bd^ 

f = modulus of rupture in pounds per square inch. 
w = total breaking load of pounds. 

/ = length of span in inches = 6. 
b — breadth of brick in inches. 
d = depth of brick in inches. 

V. Samples for test must be free from all visible ir¬ 
regularities of surface or deformities of shape, and their 
upper and lower faces must be practically parallel. 

VI. Not less than ten (io) bricks shall be broken, 
and the average of all be taken for a standard test. 


SPECIFICATIONS FOR THE STANDARD 
METHOD OF MAKING CRUSHING TESTS 
OF PAVING BRICK. 

I. The crushing test should be made on half bricks, 
loaded edgewise, or as they are laid in the street. If 
the machine used is unable to crush a full half brick, 
the area may be reduced by chipping off, keeping the 
form of the piece to be tested as nearly prismatic as 
possible. A machine of at least 100,000 pounds capac¬ 
ity should be used, and the specimens should not be re¬ 
duced below four (4) square inches of area in cross sec¬ 
tion at right angles to direction of load. 

II. The upper and lower surfaces should preferably 



45 


be ground to true and parallel planes. If this is not 
done, they should be bedded in plaster of Paris while 
in the testing machine, which should be allowed to 
harden ten minutes under the weight of the crushing 
planes only, before the load is applied. 

III. The load should be applied at a uniform rate of 
increase to the point of rupture. 

IV. Not less than an average obtained from five 
tests on five different bricks shall constitute a standard 
test. 

The following resolution was adopted: 

Whereas, from the experimental work done so far 
by this commission, or by others so far as is known to 
us, in the application of the cross breaking and crush¬ 
ing tests to paving bricks, it is not possible to show 
any close relationship between the qualities necessary 
for a good paving material and high structural strength 
as indicated by either of these tests. 

Resolved: That for this reason the commission rec¬ 
ommends that these tests shall be considered as purely 
optional in the examination of paving material, and 
not necessary as a proof of excellence. 


A HINT REGARDING THE GROUTING. 

Owing to the fact that brick pavements laid on well- 
prepared foundations of first-class material through¬ 
out have in some instances shown poor results, it would 
be well to note that the only cause for such results will 


46 


be found in the improper or insufficient grouting of the 
joints. Wherever brick pavements properly laid with 
brick of good quality have been found to show wear 
quickly it may be laid to this cause and to this cause 
alone, and it would be well for all engineers engaged 
in preparing specifications for brick paving work, or in 
superintending such work, to lay special stress upon the 
care with which such specifications are prepared, es¬ 
pecially as regards the method of preparing the. grout 
for the joints and applying the same. As regards the 
actual carrying out of the work, it is well worth while 
to take extra precautions to insure the complete filling 
of the joints with the grouting material, as well as to 
see that said material shall be properly mixed when it 
enters and fills the joints, and not separated so that 
some joints are filled with sand and some with neat 
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